Mobilizon v/s Nextcloud (v/s other?) for a network of people event calendar

I have been given the task of finding a proper platform for building a network of education, medical and other initiatives in my country, that have all the same focus (I am sorry I can't give details yet on the project, but you could probably could get a grasp of the idea if you think in something like a church whose attendants have a lot of different church-related initiatives)

Until this day, there are only isolated, individual projects, but we want a network that connects them all. So I think we will be setting up a fediverse instance for this (Still trying to decide between Pixelfed, Mastodon and Firefish), but, before that, we need to solve a simpler issue: a Calendar of Events. The idea would be that different users can add their events and all these get inside one single calendar (and you can filter by categories, etc.) Would mobilizon be the best fit for this? because at first I was thinking in making a nextcloud install, wich could satisfy the events calendar need and could also give some other services. What do you think? thanks!